diff --git a/vendor/google.golang.org/grpc/server.go b/vendor/google.golang.org/grpc/server.go
new file mode 100644
index 0000000..d705d7a
--- /dev/null
+++ b/vendor/google.golang.org/grpc/server.go
@@ -0,0 +1,1486 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"net/http"
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/trace"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/encoding/proto"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/binarylog"
+	"google.golang.org/grpc/internal/channelz"
+	"google.golang.org/grpc/internal/transport"
+	"google.golang.org/grpc/keepalive"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/stats"
+	"google.golang.org/grpc/status"
+	"google.golang.org/grpc/tap"
+)
+
+const (
+	defaultServerMaxReceiveMessageSize = 1024 * 1024 * 4
+	defaultServerMaxSendMessageSize    = math.MaxInt32
+)
+
+type methodHandler func(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor UnaryServerInterceptor) (interface{}, error)
+
+// MethodDesc represents an RPC service's method specification.
+type MethodDesc struct {
+	MethodName string
+	Handler    methodHandler
+}
+
+// ServiceDesc represents an RPC service's specification.
+type ServiceDesc struct {
+	ServiceName string
+	// The pointer to the service interface. Used to check whether the user
+	// provided implementation satisfies the interface requirements.
+	HandlerType interface{}
+	Methods     []MethodDesc
+	Streams     []StreamDesc
+	Metadata    interface{}
+}
+
+// service consists of the information of the server serving this service and
+// the methods in this service.
+type service struct {
+	server interface{} // the server for service methods
+	md     map[string]*MethodDesc
+	sd     map[string]*StreamDesc
+	mdata  interface{}
+}
+
+// Server is a gRPC server to serve RPC requests.
+type Server struct {
+	opts options
+
+	mu     sync.Mutex // guards following
+	lis    map[net.Listener]bool
+	conns  map[io.Closer]bool
+	serve  bool
+	drain  bool
+	cv     *sync.Cond          // signaled when connections close for GracefulStop
+	m      map[string]*service // service name -> service info
+	events trace.EventLog
+
+	quit               chan struct{}
+	done               chan struct{}
+	quitOnce           sync.Once
+	doneOnce           sync.Once
+	channelzRemoveOnce sync.Once
+	serveWG            sync.WaitGroup // counts active Serve goroutines for GracefulStop
+
+	channelzID int64 // channelz unique identification number
+	czData     *channelzData
+}
+
+type options struct {
+	creds                 credentials.TransportCredentials
+	codec                 baseCodec
+	cp                    Compressor
+	dc                    Decompressor
+	unaryInt              UnaryServerInterceptor
+	streamInt             StreamServerInterceptor
+	inTapHandle           tap.ServerInHandle
+	statsHandler          stats.Handler
+	maxConcurrentStreams  uint32
+	maxReceiveMessageSize int
+	maxSendMessageSize    int
+	unknownStreamDesc     *StreamDesc
+	keepaliveParams       keepalive.ServerParameters
+	keepalivePolicy       keepalive.EnforcementPolicy
+	initialWindowSize     int32
+	initialConnWindowSize int32
+	writeBufferSize       int
+	readBufferSize        int
+	connectionTimeout     time.Duration
+	maxHeaderListSize     *uint32
+}
+
+var defaultServerOptions = options{
+	maxReceiveMessageSize: defaultServerMaxReceiveMessageSize,
+	maxSendMessageSize:    defaultServerMaxSendMessageSize,
+	connectionTimeout:     120 * time.Second,
+	writeBufferSize:       defaultWriteBufSize,
+	readBufferSize:        defaultReadBufSize,
+}
+
+// A ServerOption sets options such as credentials, codec and keepalive parameters, etc.
+type ServerOption func(*options)
+
+// WriteBufferSize determines how much data can be batched before doing a write on the wire.
+// The corresponding memory allocation for this buffer will be twice the size to keep syscalls low.
+// The default value for this buffer is 32KB.
+// Zero will disable the write buffer such that each write will be on underlying connection.
+// Note: A Send call may not directly translate to a write.
+func WriteBufferSize(s int) ServerOption {
+	return func(o *options) {
+		o.writeBufferSize = s
+	}
+}
+
+// ReadBufferSize lets you set the size of read buffer, this determines how much data can be read at most
+// for one read syscall.
+// The default value for this buffer is 32KB.
+// Zero will disable read buffer for a connection so data framer can access the underlying
+// conn directly.
+func ReadBufferSize(s int) ServerOption {
+	return func(o *options) {
+		o.readBufferSize = s
+	}
+}
+
+// InitialWindowSize returns a ServerOption that sets window size for stream.
+// The lower bound for window size is 64K and any value smaller than that will be ignored.
+func InitialWindowSize(s int32) ServerOption {
+	return func(o *options) {
+		o.initialWindowSize = s
+	}
+}
+
+// InitialConnWindowSize returns a ServerOption that sets window size for a connection.
+// The lower bound for window size is 64K and any value smaller than that will be ignored.
+func InitialConnWindowSize(s int32) ServerOption {
+	return func(o *options) {
+		o.initialConnWindowSize = s
+	}
+}
+
+// KeepaliveParams returns a ServerOption that sets keepalive and max-age parameters for the server.
+func KeepaliveParams(kp keepalive.ServerParameters) ServerOption {
+	return func(o *options) {
+		o.keepaliveParams = kp
+	}
+}
+
+// KeepaliveEnforcementPolicy returns a ServerOption that sets keepalive enforcement policy for the server.
+func KeepaliveEnforcementPolicy(kep keepalive.EnforcementPolicy) ServerOption {
+	return func(o *options) {
+		o.keepalivePolicy = kep
+	}
+}
+
+// CustomCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.
+//
+// This will override any lookups by content-subtype for Codecs registered with RegisterCodec.
+func CustomCodec(codec Codec) ServerOption {
+	return func(o *options) {
+		o.codec = codec
+	}
+}
+
+// RPCCompressor returns a ServerOption that sets a compressor for outbound
+// messages.  For backward compatibility, all outbound messages will be sent
+// using this compressor, regardless of incoming message compression.  By
+// default, server messages will be sent using the same compressor with which
+// request messages were sent.
+//
+// Deprecated: use encoding.RegisterCompressor instead.
+func RPCCompressor(cp Compressor) ServerOption {
+	return func(o *options) {
+		o.cp = cp
+	}
+}
+
+// RPCDecompressor returns a ServerOption that sets a decompressor for inbound
+// messages.  It has higher priority than decompressors registered via
+// encoding.RegisterCompressor.
+//
+// Deprecated: use encoding.RegisterCompressor instead.
+func RPCDecompressor(dc Decompressor) ServerOption {
+	return func(o *options) {
+		o.dc = dc
+	}
+}
+
+// MaxMsgSize returns a ServerOption to set the max message size in bytes the server can receive.
+// If this is not set, gRPC uses the default limit.
+//
+// Deprecated: use MaxRecvMsgSize instead.
+func MaxMsgSize(m int) ServerOption {
+	return MaxRecvMsgSize(m)
+}
+
+// MaxRecvMsgSize returns a ServerOption to set the max message size in bytes the server can receive.
+// If this is not set, gRPC uses the default 4MB.
+func MaxRecvMsgSize(m int) ServerOption {
+	return func(o *options) {
+		o.maxReceiveMessageSize = m
+	}
+}
+
+// MaxSendMsgSize returns a ServerOption to set the max message size in bytes the server can send.
+// If this is not set, gRPC uses the default 4MB.
+func MaxSendMsgSize(m int) ServerOption {
+	return func(o *options) {
+		o.maxSendMessageSize = m
+	}
+}
+
+// MaxConcurrentStreams returns a ServerOption that will apply a limit on the number
+// of concurrent streams to each ServerTransport.
+func MaxConcurrentStreams(n uint32) ServerOption {
+	return func(o *options) {
+		o.maxConcurrentStreams = n
+	}
+}
+
+// Creds returns a ServerOption that sets credentials for server connections.
+func Creds(c credentials.TransportCredentials) ServerOption {
+	return func(o *options) {
+		o.creds = c
+	}
+}
+
+// UnaryInterceptor returns a ServerOption that sets the UnaryServerInterceptor for the
+// server. Only one unary interceptor can be installed. The construction of multiple
+// interceptors (e.g., chaining) can be implemented at the caller.
+func UnaryInterceptor(i UnaryServerInterceptor) ServerOption {
+	return func(o *options) {
+		if o.unaryInt != nil {
+			panic("The unary server interceptor was already set and may not be reset.")
+		}
+		o.unaryInt = i
+	}
+}
+
+// StreamInterceptor returns a ServerOption that sets the StreamServerInterceptor for the
+// server. Only one stream interceptor can be installed.
+func StreamInterceptor(i StreamServerInterceptor) ServerOption {
+	return func(o *options) {
+		if o.streamInt != nil {
+			panic("The stream server interceptor was already set and may not be reset.")
+		}
+		o.streamInt = i
+	}
+}
+
+// InTapHandle returns a ServerOption that sets the tap handle for all the server
+// transport to be created. Only one can be installed.
+func InTapHandle(h tap.ServerInHandle) ServerOption {
+	return func(o *options) {
+		if o.inTapHandle != nil {
+			panic("The tap handle was already set and may not be reset.")
+		}
+		o.inTapHandle = h
+	}
+}
+
+// StatsHandler returns a ServerOption that sets the stats handler for the server.
+func StatsHandler(h stats.Handler) ServerOption {
+	return func(o *options) {
+		o.statsHandler = h
+	}
+}
+
+// UnknownServiceHandler returns a ServerOption that allows for adding a custom
+// unknown service handler. The provided method is a bidi-streaming RPC service
+// handler that will be invoked instead of returning the "unimplemented" gRPC
+// error whenever a request is received for an unregistered service or method.
+// The handling function has full access to the Context of the request and the
+// stream, and the invocation bypasses interceptors.
+func UnknownServiceHandler(streamHandler StreamHandler) ServerOption {
+	return func(o *options) {
+		o.unknownStreamDesc = &StreamDesc{
+			StreamName: "unknown_service_handler",
+			Handler:    streamHandler,
+			// We need to assume that the users of the streamHandler will want to use both.
+			ClientStreams: true,
+			ServerStreams: true,
+		}
+	}
+}
+
+// ConnectionTimeout returns a ServerOption that sets the timeout for
+// connection establishment (up to and including HTTP/2 handshaking) for all
+// new connections.  If this is not set, the default is 120 seconds.  A zero or
+// negative value will result in an immediate timeout.
+//
+// This API is EXPERIMENTAL.
+func ConnectionTimeout(d time.Duration) ServerOption {
+	return func(o *options) {
+		o.connectionTimeout = d
+	}
+}
+
+// MaxHeaderListSize returns a ServerOption that sets the max (uncompressed) size
+// of header list that the server is prepared to accept.
+func MaxHeaderListSize(s uint32) ServerOption {
+	return func(o *options) {
+		o.maxHeaderListSize = &s
+	}
+}
+
+// NewServer creates a gRPC server which has no service registered and has not
+// started to accept requests yet.
+func NewServer(opt ...ServerOption) *Server {
+	opts := defaultServerOptions
+	for _, o := range opt {
+		o(&opts)
+	}
+	s := &Server{
+		lis:    make(map[net.Listener]bool),
+		opts:   opts,
+		conns:  make(map[io.Closer]bool),
+		m:      make(map[string]*service),
+		quit:   make(chan struct{}),
+		done:   make(chan struct{}),
+		czData: new(channelzData),
+	}
+	s.cv = sync.NewCond(&s.mu)
+	if EnableTracing {
+		_, file, line, _ := runtime.Caller(1)
+		s.events = trace.NewEventLog("grpc.Server", fmt.Sprintf("%s:%d", file, line))
+	}
+
+	if channelz.IsOn() {
+		s.channelzID = channelz.RegisterServer(&channelzServer{s}, "")
+	}
+	return s
+}
+
+// printf records an event in s's event log, unless s has been stopped.
+// REQUIRES s.mu is held.
+func (s *Server) printf(format string, a ...interface{}) {
+	if s.events != nil {
+		s.events.Printf(format, a...)
+	}
+}
+
+// errorf records an error in s's event log, unless s has been stopped.
+// REQUIRES s.mu is held.
+func (s *Server) errorf(format string, a ...interface{}) {
+	if s.events != nil {
+		s.events.Errorf(format, a...)
+	}
+}
+
+// RegisterService registers a service and its implementation to the gRPC
+// server. It is called from the IDL generated code. This must be called before
+// invoking Serve.
+func (s *Server) RegisterService(sd *ServiceDesc, ss interface{}) {
+	ht := reflect.TypeOf(sd.HandlerType).Elem()
+	st := reflect.TypeOf(ss)
+	if !st.Implements(ht) {
+		grpclog.Fatalf("grpc: Server.RegisterService found the handler of type %v that does not satisfy %v", st, ht)
+	}
+	s.register(sd, ss)
+}
+
+func (s *Server) register(sd *ServiceDesc, ss interface{}) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.printf("RegisterService(%q)", sd.ServiceName)
+	if s.serve {
+		grpclog.Fatalf("grpc: Server.RegisterService after Server.Serve for %q", sd.ServiceName)
+	}
+	if _, ok := s.m[sd.ServiceName]; ok {
+		grpclog.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
+	}
+	srv := &service{
+		server: ss,
+		md:     make(map[string]*MethodDesc),
+		sd:     make(map[string]*StreamDesc),
+		mdata:  sd.Metadata,
+	}
+	for i := range sd.Methods {
+		d := &sd.Methods[i]
+		srv.md[d.MethodName] = d
+	}
+	for i := range sd.Streams {
+		d := &sd.Streams[i]
+		srv.sd[d.StreamName] = d
+	}
+	s.m[sd.ServiceName] = srv
+}
+
+// MethodInfo contains the information of an RPC including its method name and type.
+type MethodInfo struct {
+	// Name is the method name only, without the service name or package name.
+	Name string
+	// IsClientStream indicates whether the RPC is a client streaming RPC.
+	IsClientStream bool
+	// IsServerStream indicates whether the RPC is a server streaming RPC.
+	IsServerStream bool
+}
+
+// ServiceInfo contains unary RPC method info, streaming RPC method info and metadata for a service.
+type ServiceInfo struct {
+	Methods []MethodInfo
+	// Metadata is the metadata specified in ServiceDesc when registering service.
+	Metadata interface{}
+}
+
+// GetServiceInfo returns a map from service names to ServiceInfo.
+// Service names include the package names, in the form of <package>.<service>.
+func (s *Server) GetServiceInfo() map[string]ServiceInfo {
+	ret := make(map[string]ServiceInfo)
+	for n, srv := range s.m {
+		methods := make([]MethodInfo, 0, len(srv.md)+len(srv.sd))
+		for m := range srv.md {
+			methods = append(methods, MethodInfo{
+				Name:           m,
+				IsClientStream: false,
+				IsServerStream: false,
+			})
+		}
+		for m, d := range srv.sd {
+			methods = append(methods, MethodInfo{
+				Name:           m,
+				IsClientStream: d.ClientStreams,
+				IsServerStream: d.ServerStreams,
+			})
+		}
+
+		ret[n] = ServiceInfo{
+			Methods:  methods,
+			Metadata: srv.mdata,
+		}
+	}
+	return ret
+}
+
+// ErrServerStopped indicates that the operation is now illegal because of
+// the server being stopped.
+var ErrServerStopped = errors.New("grpc: the server has been stopped")
+
+func (s *Server) useTransportAuthenticator(rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	if s.opts.creds == nil {
+		return rawConn, nil, nil
+	}
+	return s.opts.creds.ServerHandshake(rawConn)
+}
+
+type listenSocket struct {
+	net.Listener
+	channelzID int64
+}
+
+func (l *listenSocket) ChannelzMetric() *channelz.SocketInternalMetric {
+	return &channelz.SocketInternalMetric{
+		SocketOptions: channelz.GetSocketOption(l.Listener),
+		LocalAddr:     l.Listener.Addr(),
+	}
+}
+
+func (l *listenSocket) Close() error {
+	err := l.Listener.Close()
+	if channelz.IsOn() {
+		channelz.RemoveEntry(l.channelzID)
+	}
+	return err
+}
+
+// Serve accepts incoming connections on the listener lis, creating a new
+// ServerTransport and service goroutine for each. The service goroutines
+// read gRPC requests and then call the registered handlers to reply to them.
+// Serve returns when lis.Accept fails with fatal errors.  lis will be closed when
+// this method returns.
+// Serve will return a non-nil error unless Stop or GracefulStop is called.
+func (s *Server) Serve(lis net.Listener) error {
+	s.mu.Lock()
+	s.printf("serving")
+	s.serve = true
+	if s.lis == nil {
+		// Serve called after Stop or GracefulStop.
+		s.mu.Unlock()
+		lis.Close()
+		return ErrServerStopped
+	}
+
+	s.serveWG.Add(1)
+	defer func() {
+		s.serveWG.Done()
+		select {
+		// Stop or GracefulStop called; block until done and return nil.
+		case <-s.quit:
+			<-s.done
+		default:
+		}
+	}()
+
+	ls := &listenSocket{Listener: lis}
+	s.lis[ls] = true
+
+	if channelz.IsOn() {
+		ls.channelzID = channelz.RegisterListenSocket(ls, s.channelzID, lis.Addr().String())
+	}
+	s.mu.Unlock()
+
+	defer func() {
+		s.mu.Lock()
+		if s.lis != nil && s.lis[ls] {
+			ls.Close()
+			delete(s.lis, ls)
+		}
+		s.mu.Unlock()
+	}()
+
+	var tempDelay time.Duration // how long to sleep on accept failure
+
+	for {
+		rawConn, err := lis.Accept()
+		if err != nil {
+			if ne, ok := err.(interface {
+				Temporary() bool
+			}); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
+				}
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				s.mu.Lock()
+				s.printf("Accept error: %v; retrying in %v", err, tempDelay)
+				s.mu.Unlock()
+				timer := time.NewTimer(tempDelay)
+				select {
+				case <-timer.C:
+				case <-s.quit:
+					timer.Stop()
+					return nil
+				}
+				continue
+			}
+			s.mu.Lock()
+			s.printf("done serving; Accept = %v", err)
+			s.mu.Unlock()
+
+			select {
+			case <-s.quit:
+				return nil
+			default:
+			}
+			return err
+		}
+		tempDelay = 0
+		// Start a new goroutine to deal with rawConn so we don't stall this Accept
+		// loop goroutine.
+		//
+		// Make sure we account for the goroutine so GracefulStop doesn't nil out
+		// s.conns before this conn can be added.
+		s.serveWG.Add(1)
+		go func() {
+			s.handleRawConn(rawConn)
+			s.serveWG.Done()
+		}()
+	}
+}
+
+// handleRawConn forks a goroutine to handle a just-accepted connection that
+// has not had any I/O performed on it yet.
+func (s *Server) handleRawConn(rawConn net.Conn) {
+	rawConn.SetDeadline(time.Now().Add(s.opts.connectionTimeout))
+	conn, authInfo, err := s.useTransportAuthenticator(rawConn)
+	if err != nil {
+		s.mu.Lock()
+		s.errorf("ServerHandshake(%q) failed: %v", rawConn.RemoteAddr(), err)
+		s.mu.Unlock()
+		grpclog.Warningf("grpc: Server.Serve failed to complete security handshake from %q: %v", rawConn.RemoteAddr(), err)
+		// If serverHandshake returns ErrConnDispatched, keep rawConn open.
+		if err != credentials.ErrConnDispatched {
+			rawConn.Close()
+		}
+		rawConn.SetDeadline(time.Time{})
+		return
+	}
+
+	s.mu.Lock()
+	if s.conns == nil {
+		s.mu.Unlock()
+		conn.Close()
+		return
+	}
+	s.mu.Unlock()
+
+	// Finish handshaking (HTTP2)
+	st := s.newHTTP2Transport(conn, authInfo)
+	if st == nil {
+		return
+	}
+
+	rawConn.SetDeadline(time.Time{})
+	if !s.addConn(st) {
+		return
+	}
+	go func() {
+		s.serveStreams(st)
+		s.removeConn(st)
+	}()
+}
+
+// newHTTP2Transport sets up a http/2 transport (using the
+// gRPC http2 server transport in transport/http2_server.go).
+func (s *Server) newHTTP2Transport(c net.Conn, authInfo credentials.AuthInfo) transport.ServerTransport {
+	config := &transport.ServerConfig{
+		MaxStreams:            s.opts.maxConcurrentStreams,
+		AuthInfo:              authInfo,
+		InTapHandle:           s.opts.inTapHandle,
+		StatsHandler:          s.opts.statsHandler,
+		KeepaliveParams:       s.opts.keepaliveParams,
+		KeepalivePolicy:       s.opts.keepalivePolicy,
+		InitialWindowSize:     s.opts.initialWindowSize,
+		InitialConnWindowSize: s.opts.initialConnWindowSize,
+		WriteBufferSize:       s.opts.writeBufferSize,
+		ReadBufferSize:        s.opts.readBufferSize,
+		ChannelzParentID:      s.channelzID,
+		MaxHeaderListSize:     s.opts.maxHeaderListSize,
+	}
+	st, err := transport.NewServerTransport("http2", c, config)
+	if err != nil {
+		s.mu.Lock()
+		s.errorf("NewServerTransport(%q) failed: %v", c.RemoteAddr(), err)
+		s.mu.Unlock()
+		c.Close()
+		grpclog.Warningln("grpc: Server.Serve failed to create ServerTransport: ", err)
+		return nil
+	}
+
+	return st
+}
+
+func (s *Server) serveStreams(st transport.ServerTransport) {
+	defer st.Close()
+	var wg sync.WaitGroup
+	st.HandleStreams(func(stream *transport.Stream) {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			s.handleStream(st, stream, s.traceInfo(st, stream))
+		}()
+	}, func(ctx context.Context, method string) context.Context {
+		if !EnableTracing {
+			return ctx
+		}
+		tr := trace.New("grpc.Recv."+methodFamily(method), method)
+		return trace.NewContext(ctx, tr)
+	})
+	wg.Wait()
+}
+
+var _ http.Handler = (*Server)(nil)
+
+// ServeHTTP implements the Go standard library's http.Handler
+// interface by responding to the gRPC request r, by looking up
+// the requested gRPC method in the gRPC server s.
+//
+// The provided HTTP request must have arrived on an HTTP/2
+// connection. When using the Go standard library's server,
+// practically this means that the Request must also have arrived
+// over TLS.
+//
+// To share one port (such as 443 for https) between gRPC and an
+// existing http.Handler, use a root http.Handler such as:
+//
+//   if r.ProtoMajor == 2 && strings.HasPrefix(
+//   	r.Header.Get("Content-Type"), "application/grpc") {
+//   	grpcServer.ServeHTTP(w, r)
+//   } else {
+//   	yourMux.ServeHTTP(w, r)
+//   }
+//
+// Note that ServeHTTP uses Go's HTTP/2 server implementation which is totally
+// separate from grpc-go's HTTP/2 server. Performance and features may vary
+// between the two paths. ServeHTTP does not support some gRPC features
+// available through grpc-go's HTTP/2 server, and it is currently EXPERIMENTAL
+// and subject to change.
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	st, err := transport.NewServerHandlerTransport(w, r, s.opts.statsHandler)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if !s.addConn(st) {
+		return
+	}
+	defer s.removeConn(st)
+	s.serveStreams(st)
+}
+
+// traceInfo returns a traceInfo and associates it with stream, if tracing is enabled.
+// If tracing is not enabled, it returns nil.
+func (s *Server) traceInfo(st transport.ServerTransport, stream *transport.Stream) (trInfo *traceInfo) {
+	tr, ok := trace.FromContext(stream.Context())
+	if !ok {
+		return nil
+	}
+
+	trInfo = &traceInfo{
+		tr: tr,
+	}
+	trInfo.firstLine.client = false
+	trInfo.firstLine.remoteAddr = st.RemoteAddr()
+
+	if dl, ok := stream.Context().Deadline(); ok {
+		trInfo.firstLine.deadline = dl.Sub(time.Now())
+	}
+	return trInfo
+}
+
+func (s *Server) addConn(c io.Closer) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.conns == nil {
+		c.Close()
+		return false
+	}
+	if s.drain {
+		// Transport added after we drained our existing conns: drain it
+		// immediately.
+		c.(transport.ServerTransport).Drain()
+	}
+	s.conns[c] = true
+	return true
+}
+
+func (s *Server) removeConn(c io.Closer) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.conns != nil {
+		delete(s.conns, c)
+		s.cv.Broadcast()
+	}
+}
+
+func (s *Server) channelzMetric() *channelz.ServerInternalMetric {
+	return &channelz.ServerInternalMetric{
+		CallsStarted:             atomic.LoadInt64(&s.czData.callsStarted),
+		CallsSucceeded:           atomic.LoadInt64(&s.czData.callsSucceeded),
+		CallsFailed:              atomic.LoadInt64(&s.czData.callsFailed),
+		LastCallStartedTimestamp: time.Unix(0, atomic.LoadInt64(&s.czData.lastCallStartedTime)),
+	}
+}
+
+func (s *Server) incrCallsStarted() {
+	atomic.AddInt64(&s.czData.callsStarted, 1)
+	atomic.StoreInt64(&s.czData.lastCallStartedTime, time.Now().UnixNano())
+}
+
+func (s *Server) incrCallsSucceeded() {
+	atomic.AddInt64(&s.czData.callsSucceeded, 1)
+}
+
+func (s *Server) incrCallsFailed() {
+	atomic.AddInt64(&s.czData.callsFailed, 1)
+}
+
+func (s *Server) sendResponse(t transport.ServerTransport, stream *transport.Stream, msg interface{}, cp Compressor, opts *transport.Options, comp encoding.Compressor) error {
+	data, err := encode(s.getCodec(stream.ContentSubtype()), msg)
+	if err != nil {
+		grpclog.Errorln("grpc: server failed to encode response: ", err)
+		return err
+	}
+	compData, err := compress(data, cp, comp)
+	if err != nil {
+		grpclog.Errorln("grpc: server failed to compress response: ", err)
+		return err
+	}
+	hdr, payload := msgHeader(data, compData)
+	// TODO(dfawley): should we be checking len(data) instead?
+	if len(payload) > s.opts.maxSendMessageSize {
+		return status.Errorf(codes.ResourceExhausted, "grpc: trying to send message larger than max (%d vs. %d)", len(payload), s.opts.maxSendMessageSize)
+	}
+	err = t.Write(stream, hdr, payload, opts)
+	if err == nil && s.opts.statsHandler != nil {
+		s.opts.statsHandler.HandleRPC(stream.Context(), outPayload(false, msg, data, payload, time.Now()))
+	}
+	return err
+}
+
+func (s *Server) processUnaryRPC(t transport.ServerTransport, stream *transport.Stream, srv *service, md *MethodDesc, trInfo *traceInfo) (err error) {
+	if channelz.IsOn() {
+		s.incrCallsStarted()
+		defer func() {
+			if err != nil && err != io.EOF {
+				s.incrCallsFailed()
+			} else {
+				s.incrCallsSucceeded()
+			}
+		}()
+	}
+	sh := s.opts.statsHandler
+	if sh != nil {
+		beginTime := time.Now()
+		begin := &stats.Begin{
+			BeginTime: beginTime,
+		}
+		sh.HandleRPC(stream.Context(), begin)
+		defer func() {
+			end := &stats.End{
+				BeginTime: beginTime,
+				EndTime:   time.Now(),
+			}
+			if err != nil && err != io.EOF {
+				end.Error = toRPCErr(err)
+			}
+			sh.HandleRPC(stream.Context(), end)
+		}()
+	}
+	if trInfo != nil {
+		defer trInfo.tr.Finish()
+		trInfo.firstLine.client = false
+		trInfo.tr.LazyLog(&trInfo.firstLine, false)
+		defer func() {
+			if err != nil && err != io.EOF {
+				trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				trInfo.tr.SetError()
+			}
+		}()
+	}
+
+	binlog := binarylog.GetMethodLogger(stream.Method())
+	if binlog != nil {
+		ctx := stream.Context()
+		md, _ := metadata.FromIncomingContext(ctx)
+		logEntry := &binarylog.ClientHeader{
+			Header:     md,
+			MethodName: stream.Method(),
+			PeerAddr:   nil,
+		}
+		if deadline, ok := ctx.Deadline(); ok {
+			logEntry.Timeout = deadline.Sub(time.Now())
+			if logEntry.Timeout < 0 {
+				logEntry.Timeout = 0
+			}
+		}
+		if a := md[":authority"]; len(a) > 0 {
+			logEntry.Authority = a[0]
+		}
+		if peer, ok := peer.FromContext(ctx); ok {
+			logEntry.PeerAddr = peer.Addr
+		}
+		binlog.Log(logEntry)
+	}
+
+	// comp and cp are used for compression.  decomp and dc are used for
+	// decompression.  If comp and decomp are both set, they are the same;
+	// however they are kept separate to ensure that at most one of the
+	// compressor/decompressor variable pairs are set for use later.
+	var comp, decomp encoding.Compressor
+	var cp Compressor
+	var dc Decompressor
+
+	// If dc is set and matches the stream's compression, use it.  Otherwise, try
+	// to find a matching registered compressor for decomp.
+	if rc := stream.RecvCompress(); s.opts.dc != nil && s.opts.dc.Type() == rc {
+		dc = s.opts.dc
+	} else if rc != "" && rc != encoding.Identity {
+		decomp = encoding.GetCompressor(rc)
+		if decomp == nil {
+			st := status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", rc)
+			t.WriteStatus(stream, st)
+			return st.Err()
+		}
+	}
+
+	// If cp is set, use it.  Otherwise, attempt to compress the response using
+	// the incoming message compression method.
+	//
+	// NOTE: this needs to be ahead of all handling, https://github.com/grpc/grpc-go/issues/686.
+	if s.opts.cp != nil {
+		cp = s.opts.cp
+		stream.SetSendCompress(cp.Type())
+	} else if rc := stream.RecvCompress(); rc != "" && rc != encoding.Identity {
+		// Legacy compressor not specified; attempt to respond with same encoding.
+		comp = encoding.GetCompressor(rc)
+		if comp != nil {
+			stream.SetSendCompress(rc)
+		}
+	}
+
+	var payInfo *payloadInfo
+	if sh != nil || binlog != nil {
+		payInfo = &payloadInfo{}
+	}
+	d, err := recvAndDecompress(&parser{r: stream}, stream, dc, s.opts.maxReceiveMessageSize, payInfo, decomp)
+	if err != nil {
+		if st, ok := status.FromError(err); ok {
+			if e := t.WriteStatus(stream, st); e != nil {
+				grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status %v", e)
+			}
+		}
+		return err
+	}
+	if channelz.IsOn() {
+		t.IncrMsgRecv()
+	}
+	df := func(v interface{}) error {
+		if err := s.getCodec(stream.ContentSubtype()).Unmarshal(d, v); err != nil {
+			return status.Errorf(codes.Internal, "grpc: error unmarshalling request: %v", err)
+		}
+		if sh != nil {
+			sh.HandleRPC(stream.Context(), &stats.InPayload{
+				RecvTime: time.Now(),
+				Payload:  v,
+				Data:     d,
+				Length:   len(d),
+			})
+		}
+		if binlog != nil {
+			binlog.Log(&binarylog.ClientMessage{
+				Message: d,
+			})
+		}
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&payload{sent: false, msg: v}, true)
+		}
+		return nil
+	}
+	ctx := NewContextWithServerTransportStream(stream.Context(), stream)
+	reply, appErr := md.Handler(srv.server, ctx, df, s.opts.unaryInt)
+	if appErr != nil {
+		appStatus, ok := status.FromError(appErr)
+		if !ok {
+			// Convert appErr if it is not a grpc status error.
+			appErr = status.Error(codes.Unknown, appErr.Error())
+			appStatus, _ = status.FromError(appErr)
+		}
+		if trInfo != nil {
+			trInfo.tr.LazyLog(stringer(appStatus.Message()), true)
+			trInfo.tr.SetError()
+		}
+		if e := t.WriteStatus(stream, appStatus); e != nil {
+			grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status: %v", e)
+		}
+		if binlog != nil {
+			if h, _ := stream.Header(); h.Len() > 0 {
+				// Only log serverHeader if there was header. Otherwise it can
+				// be trailer only.
+				binlog.Log(&binarylog.ServerHeader{
+					Header: h,
+				})
+			}
+			binlog.Log(&binarylog.ServerTrailer{
+				Trailer: stream.Trailer(),
+				Err:     appErr,
+			})
+		}
+		return appErr
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(stringer("OK"), false)
+	}
+	opts := &transport.Options{Last: true}
+
+	if err := s.sendResponse(t, stream, reply, cp, opts, comp); err != nil {
+		if err == io.EOF {
+			// The entire stream is done (for unary RPC only).
+			return err
+		}
+		if s, ok := status.FromError(err); ok {
+			if e := t.WriteStatus(stream, s); e != nil {
+				grpclog.Warningf("grpc: Server.processUnaryRPC failed to write status: %v", e)
+			}
+		} else {
+			switch st := err.(type) {
+			case transport.ConnectionError:
+				// Nothing to do here.
+			default:
+				panic(fmt.Sprintf("grpc: Unexpected error (%T) from sendResponse: %v", st, st))
+			}
+		}
+		if binlog != nil {
+			h, _ := stream.Header()
+			binlog.Log(&binarylog.ServerHeader{
+				Header: h,
+			})
+			binlog.Log(&binarylog.ServerTrailer{
+				Trailer: stream.Trailer(),
+				Err:     appErr,
+			})
+		}
+		return err
+	}
+	if binlog != nil {
+		h, _ := stream.Header()
+		binlog.Log(&binarylog.ServerHeader{
+			Header: h,
+		})
+		binlog.Log(&binarylog.ServerMessage{
+			Message: reply,
+		})
+	}
+	if channelz.IsOn() {
+		t.IncrMsgSent()
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&payload{sent: true, msg: reply}, true)
+	}
+	// TODO: Should we be logging if writing status failed here, like above?
+	// Should the logging be in WriteStatus?  Should we ignore the WriteStatus
+	// error or allow the stats handler to see it?
+	err = t.WriteStatus(stream, status.New(codes.OK, ""))
+	if binlog != nil {
+		binlog.Log(&binarylog.ServerTrailer{
+			Trailer: stream.Trailer(),
+			Err:     appErr,
+		})
+	}
+	return err
+}
+
+func (s *Server) processStreamingRPC(t transport.ServerTransport, stream *transport.Stream, srv *service, sd *StreamDesc, trInfo *traceInfo) (err error) {
+	if channelz.IsOn() {
+		s.incrCallsStarted()
+		defer func() {
+			if err != nil && err != io.EOF {
+				s.incrCallsFailed()
+			} else {
+				s.incrCallsSucceeded()
+			}
+		}()
+	}
+	sh := s.opts.statsHandler
+	if sh != nil {
+		beginTime := time.Now()
+		begin := &stats.Begin{
+			BeginTime: beginTime,
+		}
+		sh.HandleRPC(stream.Context(), begin)
+		defer func() {
+			end := &stats.End{
+				BeginTime: beginTime,
+				EndTime:   time.Now(),
+			}
+			if err != nil && err != io.EOF {
+				end.Error = toRPCErr(err)
+			}
+			sh.HandleRPC(stream.Context(), end)
+		}()
+	}
+	ctx := NewContextWithServerTransportStream(stream.Context(), stream)
+	ss := &serverStream{
+		ctx:                   ctx,
+		t:                     t,
+		s:                     stream,
+		p:                     &parser{r: stream},
+		codec:                 s.getCodec(stream.ContentSubtype()),
+		maxReceiveMessageSize: s.opts.maxReceiveMessageSize,
+		maxSendMessageSize:    s.opts.maxSendMessageSize,
+		trInfo:                trInfo,
+		statsHandler:          sh,
+	}
+
+	ss.binlog = binarylog.GetMethodLogger(stream.Method())
+	if ss.binlog != nil {
+		md, _ := metadata.FromIncomingContext(ctx)
+		logEntry := &binarylog.ClientHeader{
+			Header:     md,
+			MethodName: stream.Method(),
+			PeerAddr:   nil,
+		}
+		if deadline, ok := ctx.Deadline(); ok {
+			logEntry.Timeout = deadline.Sub(time.Now())
+			if logEntry.Timeout < 0 {
+				logEntry.Timeout = 0
+			}
+		}
+		if a := md[":authority"]; len(a) > 0 {
+			logEntry.Authority = a[0]
+		}
+		if peer, ok := peer.FromContext(ss.Context()); ok {
+			logEntry.PeerAddr = peer.Addr
+		}
+		ss.binlog.Log(logEntry)
+	}
+
+	// If dc is set and matches the stream's compression, use it.  Otherwise, try
+	// to find a matching registered compressor for decomp.
+	if rc := stream.RecvCompress(); s.opts.dc != nil && s.opts.dc.Type() == rc {
+		ss.dc = s.opts.dc
+	} else if rc != "" && rc != encoding.Identity {
+		ss.decomp = encoding.GetCompressor(rc)
+		if ss.decomp == nil {
+			st := status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", rc)
+			t.WriteStatus(ss.s, st)
+			return st.Err()
+		}
+	}
+
+	// If cp is set, use it.  Otherwise, attempt to compress the response using
+	// the incoming message compression method.
+	//
+	// NOTE: this needs to be ahead of all handling, https://github.com/grpc/grpc-go/issues/686.
+	if s.opts.cp != nil {
+		ss.cp = s.opts.cp
+		stream.SetSendCompress(s.opts.cp.Type())
+	} else if rc := stream.RecvCompress(); rc != "" && rc != encoding.Identity {
+		// Legacy compressor not specified; attempt to respond with same encoding.
+		ss.comp = encoding.GetCompressor(rc)
+		if ss.comp != nil {
+			stream.SetSendCompress(rc)
+		}
+	}
+
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&trInfo.firstLine, false)
+		defer func() {
+			ss.mu.Lock()
+			if err != nil && err != io.EOF {
+				ss.trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				ss.trInfo.tr.SetError()
+			}
+			ss.trInfo.tr.Finish()
+			ss.trInfo.tr = nil
+			ss.mu.Unlock()
+		}()
+	}
+	var appErr error
+	var server interface{}
+	if srv != nil {
+		server = srv.server
+	}
+	if s.opts.streamInt == nil {
+		appErr = sd.Handler(server, ss)
+	} else {
+		info := &StreamServerInfo{
+			FullMethod:     stream.Method(),
+			IsClientStream: sd.ClientStreams,
+			IsServerStream: sd.ServerStreams,
+		}
+		appErr = s.opts.streamInt(server, ss, info, sd.Handler)
+	}
+	if appErr != nil {
+		appStatus, ok := status.FromError(appErr)
+		if !ok {
+			appStatus = status.New(codes.Unknown, appErr.Error())
+			appErr = appStatus.Err()
+		}
+		if trInfo != nil {
+			ss.mu.Lock()
+			ss.trInfo.tr.LazyLog(stringer(appStatus.Message()), true)
+			ss.trInfo.tr.SetError()
+			ss.mu.Unlock()
+		}
+		t.WriteStatus(ss.s, appStatus)
+		if ss.binlog != nil {
+			ss.binlog.Log(&binarylog.ServerTrailer{
+				Trailer: ss.s.Trailer(),
+				Err:     appErr,
+			})
+		}
+		// TODO: Should we log an error from WriteStatus here and below?
+		return appErr
+	}
+	if trInfo != nil {
+		ss.mu.Lock()
+		ss.trInfo.tr.LazyLog(stringer("OK"), false)
+		ss.mu.Unlock()
+	}
+	err = t.WriteStatus(ss.s, status.New(codes.OK, ""))
+	if ss.binlog != nil {
+		ss.binlog.Log(&binarylog.ServerTrailer{
+			Trailer: ss.s.Trailer(),
+			Err:     appErr,
+		})
+	}
+	return err
+}
+
+func (s *Server) handleStream(t transport.ServerTransport, stream *transport.Stream, trInfo *traceInfo) {
+	sm := stream.Method()
+	if sm != "" && sm[0] == '/' {
+		sm = sm[1:]
+	}
+	pos := strings.LastIndex(sm, "/")
+	if pos == -1 {
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&fmtStringer{"Malformed method name %q", []interface{}{sm}}, true)
+			trInfo.tr.SetError()
+		}
+		errDesc := fmt.Sprintf("malformed method name: %q", stream.Method())
+		if err := t.WriteStatus(stream, status.New(codes.ResourceExhausted, errDesc)); err != nil {
+			if trInfo != nil {
+				trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+				trInfo.tr.SetError()
+			}
+			grpclog.Warningf("grpc: Server.handleStream failed to write status: %v", err)
+		}
+		if trInfo != nil {
+			trInfo.tr.Finish()
+		}
+		return
+	}
+	service := sm[:pos]
+	method := sm[pos+1:]
+
+	if srv, ok := s.m[service]; ok {
+		if md, ok := srv.md[method]; ok {
+			s.processUnaryRPC(t, stream, srv, md, trInfo)
+			return
+		}
+		if sd, ok := srv.sd[method]; ok {
+			s.processStreamingRPC(t, stream, srv, sd, trInfo)
+			return
+		}
+	}
+	// Unknown service, or known server unknown method.
+	if unknownDesc := s.opts.unknownStreamDesc; unknownDesc != nil {
+		s.processStreamingRPC(t, stream, nil, unknownDesc, trInfo)
+		return
+	}
+	if trInfo != nil {
+		trInfo.tr.LazyLog(&fmtStringer{"Unknown service %v", []interface{}{service}}, true)
+		trInfo.tr.SetError()
+	}
+	errDesc := fmt.Sprintf("unknown service %v", service)
+	if err := t.WriteStatus(stream, status.New(codes.Unimplemented, errDesc)); err != nil {
+		if trInfo != nil {
+			trInfo.tr.LazyLog(&fmtStringer{"%v", []interface{}{err}}, true)
+			trInfo.tr.SetError()
+		}
+		grpclog.Warningf("grpc: Server.handleStream failed to write status: %v", err)
+	}
+	if trInfo != nil {
+		trInfo.tr.Finish()
+	}
+}
+
+// The key to save ServerTransportStream in the context.
+type streamKey struct{}
+
+// NewContextWithServerTransportStream creates a new context from ctx and
+// attaches stream to it.
+//
+// This API is EXPERIMENTAL.
+func NewContextWithServerTransportStream(ctx context.Context, stream ServerTransportStream) context.Context {
+	return context.WithValue(ctx, streamKey{}, stream)
+}
+
+// ServerTransportStream is a minimal interface that a transport stream must
+// implement. This can be used to mock an actual transport stream for tests of
+// handler code that use, for example, grpc.SetHeader (which requires some
+// stream to be in context).
+//
+// See also NewContextWithServerTransportStream.
+//
+// This API is EXPERIMENTAL.
+type ServerTransportStream interface {
+	Method() string
+	SetHeader(md metadata.MD) error
+	SendHeader(md metadata.MD) error
+	SetTrailer(md metadata.MD) error
+}
+
+// ServerTransportStreamFromContext returns the ServerTransportStream saved in
+// ctx. Returns nil if the given context has no stream associated with it
+// (which implies it is not an RPC invocation context).
+//
+// This API is EXPERIMENTAL.
+func ServerTransportStreamFromContext(ctx context.Context) ServerTransportStream {
+	s, _ := ctx.Value(streamKey{}).(ServerTransportStream)
+	return s
+}
+
+// Stop stops the gRPC server. It immediately closes all open
+// connections and listeners.
+// It cancels all active RPCs on the server side and the corresponding
+// pending RPCs on the client side will get notified by connection
+// errors.
+func (s *Server) Stop() {
+	s.quitOnce.Do(func() {
+		close(s.quit)
+	})
+
+	defer func() {
+		s.serveWG.Wait()
+		s.doneOnce.Do(func() {
+			close(s.done)
+		})
+	}()
+
+	s.channelzRemoveOnce.Do(func() {
+		if channelz.IsOn() {
+			channelz.RemoveEntry(s.channelzID)
+		}
+	})
+
+	s.mu.Lock()
+	listeners := s.lis
+	s.lis = nil
+	st := s.conns
+	s.conns = nil
+	// interrupt GracefulStop if Stop and GracefulStop are called concurrently.
+	s.cv.Broadcast()
+	s.mu.Unlock()
+
+	for lis := range listeners {
+		lis.Close()
+	}
+	for c := range st {
+		c.Close()
+	}
+
+	s.mu.Lock()
+	if s.events != nil {
+		s.events.Finish()
+		s.events = nil
+	}
+	s.mu.Unlock()
+}
+
+// GracefulStop stops the gRPC server gracefully. It stops the server from
+// accepting new connections and RPCs and blocks until all the pending RPCs are
+// finished.
+func (s *Server) GracefulStop() {
+	s.quitOnce.Do(func() {
+		close(s.quit)
+	})
+
+	defer func() {
+		s.doneOnce.Do(func() {
+			close(s.done)
+		})
+	}()
+
+	s.channelzRemoveOnce.Do(func() {
+		if channelz.IsOn() {
+			channelz.RemoveEntry(s.channelzID)
+		}
+	})
+	s.mu.Lock()
+	if s.conns == nil {
+		s.mu.Unlock()
+		return
+	}
+
+	for lis := range s.lis {
+		lis.Close()
+	}
+	s.lis = nil
+	if !s.drain {
+		for c := range s.conns {
+			c.(transport.ServerTransport).Drain()
+		}
+		s.drain = true
+	}
+
+	// Wait for serving threads to be ready to exit.  Only then can we be sure no
+	// new conns will be created.
+	s.mu.Unlock()
+	s.serveWG.Wait()
+	s.mu.Lock()
+
+	for len(s.conns) != 0 {
+		s.cv.Wait()
+	}
+	s.conns = nil
+	if s.events != nil {
+		s.events.Finish()
+		s.events = nil
+	}
+	s.mu.Unlock()
+}
+
+// contentSubtype must be lowercase
+// cannot return nil
+func (s *Server) getCodec(contentSubtype string) baseCodec {
+	if s.opts.codec != nil {
+		return s.opts.codec
+	}
+	if contentSubtype == "" {
+		return encoding.GetCodec(proto.Name)
+	}
+	codec := encoding.GetCodec(contentSubtype)
+	if codec == nil {
+		return encoding.GetCodec(proto.Name)
+	}
+	return codec
+}
+
+// SetHeader sets the header metadata.
+// When called multiple times, all the provided metadata will be merged.
+// All the metadata will be sent out when one of the following happens:
+//  - grpc.SendHeader() is called;
+//  - The first response is sent out;
+//  - An RPC status is sent out (error or success).
+func SetHeader(ctx context.Context, md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	return stream.SetHeader(md)
+}
+
+// SendHeader sends header metadata. It may be called at most once.
+// The provided md and headers set by SetHeader() will be sent.
+func SendHeader(ctx context.Context, md metadata.MD) error {
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	if err := stream.SendHeader(md); err != nil {
+		return toRPCErr(err)
+	}
+	return nil
+}
+
+// SetTrailer sets the trailer metadata that will be sent when an RPC returns.
+// When called more than once, all the provided metadata will be merged.
+func SetTrailer(ctx context.Context, md metadata.MD) error {
+	if md.Len() == 0 {
+		return nil
+	}
+	stream := ServerTransportStreamFromContext(ctx)
+	if stream == nil {
+		return status.Errorf(codes.Internal, "grpc: failed to fetch the stream from the context %v", ctx)
+	}
+	return stream.SetTrailer(md)
+}
+
+// Method returns the method string for the server context.  The returned
+// string is in the format of "/service/method".
+func Method(ctx context.Context) (string, bool) {
+	s := ServerTransportStreamFromContext(ctx)
+	if s == nil {
+		return "", false
+	}
+	return s.Method(), true
+}
+
+type channelzServer struct {
+	s *Server
+}
+
+func (c *channelzServer) ChannelzMetric() *channelz.ServerInternalMetric {
+	return c.s.channelzMetric()
+}